I'm no engineer either, but I think your wrong. At least in general, if you level a tank stand it's because you put stuff under it so there effectively are no "high spots" hence no pressure points. In fact that's what the stand apparently tries to do with 20+ leveling feet around the perimeter, instead of just one at each corner, it distributes the load to more places. So if you distribute the load you reduce the "pressure points", putting down composite decking could have done just that... but again depending upon how it was done.That’s not the best solution at all. You’ll still have pressure points at the high spots. Might level it but will create uneven load.
If I’m wrong someone correct me. I’m no engineer.